Air Force Staff Sgt. Ben Jacobs, the coalition gunner/flight engineer, mouthed the word “down,” motioning with both thumbs, and for a second, it seemed the aircraft was out of control.

The helicopter finally leveled off in this exercise, designed to teach crews how to react to ground fire. The “aerial escort” mission, in which Afghan crews fly in two-ship formations, is something they will have to master to provide close air support and coordinate with Afghan soldiers to attack enemy forces on the ground.

This was just one of several training sessions per week at Kandahar Air Field by the 738th Air Expeditionary Advisory Squadron, which is tasked with training and advising the Afghan air force’s Kandahar Air Wing. Afghan pilots flew 70 percent of the training mission, said Air Force Capt. Jeremy Powell, an adviser pilot with the 738th.

Coalition advisers planned the two-hour mission and led a pre-mission briefing, but an Afghan intelligence officer and several Afghan crew members also briefed, with advisers quizzing them about what to do in case of contingencies. The two Afghan pilots were proficient in English, but interpreters jumped in often to translate, especially for the rest of the crew.

With only 18 months left to go before NATO ends its combat mission and much of its air support, coalition trainers are teaching the Afghan air force how to fly and maintain aircraft, and secure airfields as fast and as much as they can before coalition combat troops leave, along with much of its air power.

In a landlocked country roughly the size of Texas, where towns and cities are separated by vast expanses of mountain and desert, an air force is crucial to sustaining the 350,000 Afghan ground troops stationed at remote bases who will continue fighting the estimated 20,000 to 30,000 Taliban insurgents in the country long after coalition troops leave.

Tasked with the mission are about 940 coalition trainers, most of whom will stay through 2017 because of technological challenges, especially for a country where 60 percent to 70 percent of the population is illiterate in its own languages.

To become pilots, Afghans must undergo about two years of training: one year of English immersion, six months of basic flight school, two months of advanced flight drills, then months more experience to qualify for specific missions.

Currently, 128 pilots are being trained, compared with 98 who are operational. One of the pilots undergoing training is 21-year-old 2nd Lt. Niloofar Rhmani, the first woman in 30 years to be trained to fly in Afghanistan.

The most difficult challenge for the trainers by 2017 will be bringing Afghan aircraft maintenance crews up to international standards, coalition officials say.

“When you go down the road to try to introduce language to help resolve some of our maintenance standardization issues, when you’re trying to overcome a generation of illiteracy, when you’re trying to overcome a generation of technical incompetence, and you’re trying to introduce technical competence, it takes time to do that,” said Air Force Col. James Brandenburg, commander of the 738th Air Expeditionary Advisory Group training the Afghan Air Force’s Kandahar Air Wing.

From 2017 through 2024, a smaller yet unspecified number of the 940 coalition advisers will remain and move from training the Afghan Air Force on tactics to advising Afghan commanders on strategy.

The training mission is on track, said Air Force Brig. Gen. Steven M. Shepro, commanding general of NATO Air Training Command Afghanistan.

The Afghan air force has roughly 6,400 members spread across three air wings, based in Kabul, Kandahar and Shindand, with detachments in Mazar-e-Sharif, Herat and Jalalabad.

So far, it can field only about half a dozen transport helicopter crews that can conduct resupply, casualty evacuation and air assault missions without coalition advisers. None of the fixed-wing plane crews can conduct missions without advisers because of the lack of crew commanders, but the first two will be trained by July.

Coalition officials hope there will eventually be as many independent crews as there are planes.

This month, Mi-35 crews will begin providing “armed overwatch,” a step toward close air support during which they will observe ground troops and help if necessary. This winter, the Afghan air force will develop basic night-flying capabilities, Gen. Shepro said.

In the autumn of 2014, the Afghan air force will receive the first of 20 A-29 Super Tucano turboprop aircraft to train for close air support missions with Afghan ground forces, but they are not expected to be fully operational until 2015. Afghan pilots also will begin training on C-130 medium-lift cargo planes this summer.

Back at headquarters, the crews of the aerial escort training mission held a 20-minute debrief, led by Air Force Lt. Col. Paul Lawrenz, operations commander for the 441st Air Expeditionary Advisory Squadron.

“I didn’t see anything significant that was a safety problem or a big issue that we didn’t overcome,” Col. Lawrenz, who advised the other Mi-17 crew, told the tired Afghan crew members through translators at the Kandahar Air Field.

“I want you guys to do the lead changes, though,” he said. “I need you guys to come on the radio and start doing all the radio calls yourself.

“Make the communications as effective as possible. Say where the threat is; it’s not just ‘breaking left.’ It’s a good thing to get initially, but what is it you’re breaking left for? Is it terrain? Is it a bird? Whatever it is, you need to specify what you’re breaking for.”

Across the country, coalition and Afghan officials are emphasizing to their trainees that they soon will be leading missions by themselves, in far more dangerous conditions.

“Having all these U.S., coalition forces, advisers, instructors and contractors around us is a golden opportunity for all of us,” Gen. Shir-Mohammad Karimi, the Afghan National Army chief of staff, told 13 basic flight school graduates at a ceremony in May at the Shindand Air Base.

“One day, they all will return to their homes, and you will be left with all the responsibility on your shoulders. Make sure you do not [squander] learning enough skills from them for working independently. Learning and gaining knowledge never ends,” he said.